THE GREAT PACIFIC CLEAN-UP

The great Pacific clean-up: Weighing the benefits of removing ocean plastic. A new study examines how cleaning up the North Pacific Garbage Patch would benefit marine life – but at what cost to the climate? 

Between California and Hawaii lies one of the most infamous symbols of humanity’s plastic problem: the North Pacific Garbage Patch (NPGP). This floating mass of debris, concentrated in the subtropical gyre, has become a hotspot for plastic pollution research and clean-up efforts. But, as organisations develop technologies to remove this legacy pollution, a critical question emerges: do the benefits of clean-up outweigh the environmental costs?

A comprehensive new study co-authored by a group of international experts including Plymouth Marine Laboratory (PML’s) Dr Samantha Garrard and published in Scientific Reports provides the first rigorous assessment of this trade-off, examining whether removing plastic from the NPGP would truly help – or potentially harm – the marine ecosystem.

The Scale of the North Pacific Garbage Patch (NPGP)  

The NPGP contains an estimated 45,000 to 129,000 tons of floating plastic debris, with current concentrations averaging 72-83 kilograms per square kilometre. The majority of this plastic originates from fishing activities, including abandoned, lost, or discarded fishing gear that continues to trap and kill marine life through “ghost fishing.”

But the problem extends beyond the visible debris. Large plastic items continuously fragment into smaller microplastics, which disperse throughout the water column and can persist for decades or centuries. These microplastics pose different but equally concerning risks to marine life, from ingestion by zooplankton to potential interference with ocean carbon cycling.

The study’s modelling reveals a troubling trajectory: without intervention, macroplastic concentrations could reach 86-140 kg/km² by 2040, far exceeding safe levels for marine mammals, sea turtles, and seabirds.

Measuring the Impact

“With this work, we set a precedent for how environmentally sound removal of existing plastic pollution can be defined in practice.” [excerpt from the paper].

The researcher team developed a comprehensive framework to assess the vulnerability of nine key groups of marine life – including zooplankton, fish, sea turtles, seabirds, and marine mammals – to three different stressors: macroplastics, microplastics, and clean-up activities themselves.

Their analysis revealed that marine life faces greater threats from plastic pollution than from clean-up operations. On a vulnerability scale of 1 (low) to 3 (high), microplastics scored highest at 2.3, followed by macroplastics at 1.9, while clean-up activities scored lowest at 1.8.

The difference lies largely in scope and duration. While clean-up operations would be geographically limited and temporary (5-10 years), plastic pollution affects vast areas and persists for decades. Macroplastics that escape from the NPGP wash up on Hawaiian shores, while microplastics sink into deep ocean waters, extending the pollution’s impact far beyond the garbage patch itself.

The Ocean Clean-up Case Study

The research team examined The Ocean Clean-up‘s System 03 technology as a real-world case study. This innovative system uses a 2.2-kilometer floating barrier towed between two slow-moving vessels to collect plastic debris. The system targets areas with the highest plastic concentrations and uses artificial intelligence to optimise collection routes.
Over 18 cleanup campaigns between July 2021 and November 2023, the technology demonstrated its effectiveness while providing crucial data on environmental interactions. The system primarily catches fish (84% of incidental catch by count), but notably, most are coastal species that may actually be invasive in the open ocean environment.

More concerning are encounters with threatened species like sea turtles, though researchers found these animals often had already ingested plastic or were trapped in debris – suggesting clean-up operations might actually rescue some individuals.

Climate Costs and Carbon Calculations

Clean-up operations come with their own environmental price tag, primarily through vessel fuel consumption. The study estimates that a full-scale 10-year clean-up would emit 0.4 to 2.9 million metric tons of carbon, depending on operational efficiency improvements.

However, this cost may be offset by preventing larger climate impacts. The research reveals that microplastics in the NPGP could reduce the ocean’s ability to absorb carbon by interfering with zooplankton grazing and other biological processes. This disruption to the biological carbon pump could result in 15-30 million metric tons of reduced carbon sequestration annually- potentially far outweighing clean-up emissions.

Additionally, the plastic debris itself releases greenhouse gases through photodegradation when exposed to UV radiation, though these emissions are relatively small compared to vessel operations.

The Path to Recovery

The study’s ecological risk modelling provides clear benchmarks for success. An 80% reduction in macroplastics would bring concentrations within safe levels for marine mammals and sea turtles, though seabirds would remain at elevated risk. Even a 50% clean-up under certain scenarios could significantly reduce entanglement risks.

For microplastics, the benefits are more limited in the short term. Since most microplastics in the NPGP come from external sources rather than local fragmentation, concentrations would remain above concerning thresholds even after clean-up. However, removing macroplastics would prevent additional microplastic generation over time.

Species-Specific Considerations

The study identifies particular concerns and benefits for different marine life:

Winners from clean-up:

• Marine mammals show lower vulnerability to clean-up than to plastic pollution
• Zooplankton face significant microplastic impacts that clean-up could eventually reduce
• Some sea turtles may be rescued from entanglement during operations

Requiring careful attention:

• Sea turtles, sharks, and fish show medium vulnerability to clean-up activities
• Seabirds remain at high risk from plastic pollution even after substantial clean-up
• Neuston (surface-dwelling organisms) need monitoring during operations

Potential losers:

• Octopuses and some coastal species that use plastic debris as habitat
• However, many of these “rafting species” are actually invasive coastal organisms transported to the open ocean
• While clean-up provides immediate benefits, the researchers emphasise that removing legacy pollution is only part of the solution. The study advocates for parallel efforts to reduce plastic production and prevent new pollution from reaching the ocean.

For the NPGP specifically, this means addressing plastic emissions from land-based sources and industrial fishing activities, while also cleaning beaches and intercepting river plastic before it reaches the ocean. Clean-up operations also provide valuable data on plastic sources and composition, informing upstream prevention strategies.

This research establishes the first comprehensive framework for evaluating “environmentally sound” plastic clean-up. The methodology can be adapted to assess clean-up projects in other marine environments and different technologies.

The framework acknowledges significant uncertainties, particularly regarding climate impacts and ecosystem interactions. The researchers recommend periodic reassessment as new data becomes available and advocate for similar analyses of clean-up approaches in other environments.

“This research represents a crucial step toward evidence-based decision-making in ocean clean-up efforts, providing a practical example of how environmental impact assessments can guide clean-up activities and ensure their net benefit to the environment.” says Dr Samantha Garrard.

“The North Pacific Garbage Patch remains a sobering symbol of humanity’s plastic problem, and while the top priority needs to be preventing plastic from entering the Ocean, it is also clear that carefully managed clean-up efforts could begin to address the legacy of decades of ocean pollution, buying time for the upstream changes needed to prevent future accumulation.”

Dr. Matthias Egger, Director of Environmental and Social Affairs at The Ocean Clean-up said:

“This study introduces the first comprehensive framework to assess whether large-scale ocean clean-ups deliver a net environmental benefit. Our findings show that, when done with proper safeguards, cleaning up the North Pacific Garbage Patch benefits marine life more than it harms it.

Prevention is key — but removing legacy plastic can protect threatened species, avert greater microplastic and climate impacts, guide smarter policies to stop future pollution, and provide a unique platform for cutting-edge ocean research.”

Image: Plastic catch onboard the support vessels of System 03. Image credit: The Ocean Cleanup.

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